Organic light emitting display panel and method of manufacturing the same

ABSTRACT

Provided are an organic light emitting display panel and a method of manufacturing the same. The organic light emitting display panel includes: a pixel defined by an intersection of one of a plurality of data lines and one of a plurality of gate lines, the pixel including: a transistor, a storage capacitor including: a first electrode, and a second electrode, and a semiconductor layer, a first plate partially overlapping the semiconductor layer in the pixel, the first plate including: a gate portion of the transistor, and a capacitor-forming portion including the first electrode of the storage capacitor, and a second plate on the first plate in the pixel, the second plate including the second electrode of the storage capacitor, the second plate not overlapping the semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims benefit and priority under 35 U.S.C.§119(a) of Korean Patent Application No. 10-2014-0097297, filed on Jul.30, 2014, the entire disclosure of which is hereby incorporated byreference herein for all purposes.

BACKGROUND

1. Technical Field

The following description relates to an organic light emitting displaypanel and a method of manufacturing the same.

2. Discussion of the Related Art

In the field of flat display devices, liquid crystal display deviceshave been widely used due to their relatively light weight and low powerconsumption. However, because the liquid crystal display device is anon-emissive device that cannot emit light by itself, it has limitationsin brightness, contrast ratio, viewing angle, and screen size.

Accordingly, development of new types of flat display devices is inprogress to address the limitations of the typical liquid crystaldisplay devices. An organic light emitting display device, one of thenew types of flat display devices, is an emissive device that is able toemit light by itself (“self-emissive”), so the organic light emittingdisplay device may provide higher brightness, a wider viewing angle, andan improved contrast ratio, compared to the liquid crystal displaydevice. Furthermore, because the organic light emitting display devicedoes not require a backlight, it is advantageous for making lightweightand thin displays, as well as for saving on power consumption.

An organic light emitting display panel of the organic light emittingdisplay device displays images by using light emitted from an organiclight emitting element that is connected with a thin film transistor ofeach pixel area. In the organic light emitting element, an organic lightemitting layer made of an organic material between an anode and acathode emits a light by applying an electric field thereto. The organiclight emitting display panel has features including a low drivingvoltage, low power consumption, and light weight. Further, the organiclight emitting display panel can be applied on a flexible substrate.

However, the organic light emitting display panel may bring about anincrease in driving voltage and leakage current due to degradation inthe electric property of the transistor to thereby create black dots onthe panel.

SUMMARY

Accordingly, embodiments of the present application are directed to anorganic light emitting display panel and a method of manufacturing thesame that substantially obviate one or more problems due to limitationsand disadvantages of the related art.

An object of embodiments is to provide an organic light emitting displaypanel by which degradation of the electric property of the transistormay be prevented to thereby reduce the driving voltage and leakagecurrent and prevent the creation of the black dots.

Additional advantages, objects, and features of the disclosure will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose according to one aspect of the invention, there is provided anorganic light emitting display panel, including: a pixel defined by anintersection of one of a plurality of data lines and one of a pluralityof gate lines, the pixel including: a transistor, a storage capacitorincluding: a first electrode, and a second electrode, and asemiconductor layer, a first plate partially overlapping thesemiconductor layer in the pixel, the first plate including: a gateportion of the transistor, and a capacitor-forming portion including thefirst electrode of the storage capacitor, and a second plate on thefirst plate in the pixel, the second plate including the secondelectrode of the storage capacitor, the second plate not overlapping thesemiconductor layer.

In another aspect, there is provided a method of manufacturing anorganic light emitting display panel, the method including: providing apixel defined by an intersection of one of a plurality of data lines andone of a plurality of gate lines, the providing the pixel including:providing a transistor, providing a storage capacitor including: a firstelectrode, and a second electrode, and providing a semiconductor layer,providing a first plate partially overlapping the semiconductor layer inthe pixel, the providing a first plate including: providing a gateportion of the transistor, and providing a capacitor-forming portionincluding the first electrode of the storage capacitor, and providing asecond plate on the first plate in the pixel, the second plate includingthe second electrode of the storage capacitor, the second plate notoverlapping the semiconductor layer.

Other systems, methods, features and advantages will be, or will become,apparent to one with skill in the art upon examination of the followingfigures and detailed description. It is intended that all suchadditional systems, methods, features and advantages be included withinthis description, be within the scope of the present disclosure, and beprotected by the following claims. Nothing in this section should betaken as a limitation on those claims. Further aspects and advantagesare discussed below in conjunction with the embodiments. It is to beunderstood that both the foregoing general description and the followingdetailed description of the present disclosure are examples andexplanatory, and are intended to provide further explanation of thedisclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate implementations of the inventionand together with the description serve to explain the principles of theinvention.

FIG. 1 illustrates a block diagram of a system configuration of anorganic light emitting display device according to an embodiment.

FIG. 2 illustrates a circuit diagram of an example of a pixel structureof an organic light emitting display panel according to an embodiment.

FIG. 3 illustrates a circuit diagram of an example of a pixel structureof an organic light emitting display panel according to an embodiment.

FIG. 4 illustrates a circuit diagram of a common part in various examplepixel structures of an organic light emitting display panel according toan embodiment.

FIG. 5 is a partial plan view illustrating a pixel of an organic lightemitting display panel 140 according to an embodiment.

FIG. 6 illustrates a partial structure of the first plate 530 in thepixel of the organic light emitting display panel 140 of FIG. 5.

FIG. 7 is a partial sectional view of a pixel of an organic lightemitting display panel according to an embodiment.

FIG. 8 is a partial sectional view of a pixel of an organic lightemitting display panel according to an embodiment.

FIG. 9 is a partial sectional view of a pixel of an organic lightemitting display panel according to an embodiment.

FIGS. 10A and 10B illustrate partial sectional views of a structure ofthe second plate in the pixel of the organic light emitting displaypanel according to an embodiment.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals should be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. In the following description, when a detailed description ofwell-known functions or configurations related to this document isdetermined to unnecessarily cloud a gist of the invention, the detaileddescription thereof will be omitted. The progression of processing stepsand/or operations described is an example; however, the sequence ofsteps and/or operations is not limited to that set forth herein and maybe changed as is known in the art, with the exception of steps and/oroperations necessarily occurring in a certain order. Like referencenumerals designate like elements throughout. Names of the respectiveelements used in the following explanations are selected only forconvenience of writing the specification and may be thus different fromthose used in actual products.

In the description of embodiments, when a structure is described asbeing positioned “on or above” or “under or below” another structure,this description should be construed as including a case in which thestructures contact each other as well as a case in which a thirdstructure is disposed therebetween.

Hereinafter, embodiments will be described in detail with reference tothe accompanying drawings.

FIG. 1 illustrates a block diagram of a system configuration of anorganic light emitting display device according to an embodiment.

With reference to FIG. 1, the organic light emitting display device 100may include an organic light emitting display panel 140, a data drivingunit 120, a gate driving unit 130, and a timing controller 110. First,the timing controller 110 may output a data control signal DCS forcontrolling the data driving unit 120 and a gate control signal GCS forcontrolling the gate driving unit 130. The data control signal DCS andgate control signal GCS may be based on external timing signals, such asvertical/horizontal synchronization signals Vsync and Hsync and imagedata DATA input from a host system, a clock signal CLK, or the like.Further, the timing controller 110 may transform the image data DATAinput from the host system into data signals to be used in the datadriving unit 120, and may supply the transformed image data DATA′ to thedata driving unit 120.

In response to data control signals DCS and the transformed image dataDATA′, which may be input from the timing controller 110, the datadriving unit 120 may transform the image data DATA′ into data signals(analog pixel signals or data voltages), which are voltagescorresponding to gradation, to supply the same to data lines D1 to Dm.The gate driving unit 130 may supply scan signals (gate pulses, scanpulses or gate-on-signals) to gate lines Gl to Gn in sequence, inresponse to the gate control signals GCS input from the timingcontroller 110.

Meanwhile, a pixel P on the organic light emitting display panel 140 maybe provided in a pixel area defined by the data lines Dl to Dm and thegate lines Gl to Gn in a matrix, and may be at least one organic lightemitting element including a pixel electrode (e.g., an anode) as thefirst electrode, a common electrode (e.g., a cathode) as the secondelectrode, and an organic layer. Each pixel P may be provided with agate line Gl to Gn, a data line Dl to Dm, and a high voltage line forsupplying a high voltage. Further, a switching transistor may beprovided between the gate lines Gl to Gn and the data lines Dl to Dm ineach pixel. Further, an organic light emitting diode (which may includean anode, a cathode, and an organic light emitting layer) and a drivingtransistor (between the a source electrode (or drain electrode) of theswitching transistor and the high voltage line) are formed in the pixel.

In the driving transistor of the organic light emitting display panel140 according to an embodiment, the first plate that is positioned on asemiconductor layer may overlap the semiconductor layer at least inpart. However, the second plate, which is positioned on the first plateand forms a storage capacitor together with the first plate, does notoverlap the semiconductor layer, which will be described in detailbelow.

FIG. 2 illustrates a circuit diagram of an example of a pixel structureof an organic light emitting display panel 140 according to anembodiment.

FIG. 2 shows an example of an equivalent circuit diagram of a structureof two transistors (i.e., “2T”) and one capacitor (i.e., “1C”). Withreference to FIG. 2, each pixel may be connected with a single data lineDL, and may receive a single scan signal SCAN through the single gateline GL.

The pixel may include an organic light emitting diode OLED, a drivingtransistor DT, a switching transistor SWT, and a storage capacitor Cstg.As set forth above, each pixel may have a 2T-1C structure in which twotransistors DT, SWT and one storage capacitor Cstg are provided. Thedriving transistor DT in each pixel may be applied with a drivingvoltage EVDD from a driving voltage line (DVL), and may drive theorganic light emitting diode OLED under the control by a voltage (datavoltage) of a gate node N2, which may be applied through the switchingtransistor SWT.

The driving transistor DT may be connected to the first node N1, thesecond node N2, and the third node N3. The first node N1 may beconnected with the switching transistor SWT, and the second node N2 maybe connected with the driving transistor DT. Further, the third node N3may be supplied with the driving voltage EVDD. The pixel structure ofthe organic light emitting display panel 140, according to embodiments,is not limited to the above 2T-1C structure, and may be, for example, a3T-1C structure, which will be described with reference to FIG. 3.

FIG. 3 illustrates a circuit diagram of an example of a pixel structureof an organic light emitting display panel 140 according to anembodiment.

With reference to the FIG. 3 example showing a 3T-1C structure, thepixel structure may include an organic light emitting diode OLED, adriving transistor DT, a switching transistor SWT, a sensing transistorSENT, and a storage capacitor Cstg. The driving transistor DT in eachpixel may be applied with a driving voltage EVDD from a driving voltageline (DVL), and may drive the organic light emitting diode OLED underthe control of a voltage (data voltage) of a gate node N2 appliedthrough the switching transistor SWT.

The driving transistor DT may be connected to the first node N1, thesecond node N2, and the third node N3. The first node N1 may beconnected with the sensing transistor SENT, and the second node N2 maybe connected with the switching transistor SWT. Further, the third nodeN3 may be supplied with the driving voltage EVDD.

As an example, the first node of the driving transistor DT may be, e.g.,a source node (or referred to as a “source electrode”), and the secondnode thereof may be a gate node (or referred to as a “gate electrode”).Further, the third node N3 of the driving transistor DT may be a drainnode (or referred to as a “drain electrode”). The first node, the secondnode and the third node of the driving transistor DT may be changedaccording to the change in the type and circuits of the transistor.

In addition, the sensing transistor SENT may be controlled by a scansignal SCAN supplied from the gate line GL, and may be connected betweenthe first node N1 of the driving transistor DT and either the referencevoltage line (RVL) for supplying the reference voltage or a connectionpattern (CP) connected with the reference voltage line (RVL). Inaddition, the switching transistor SWT may be controlled by a commonscan signal SCAN supplied from the gate line GL, and may be connectedbetween the corresponding data line DL and the second node N2 of thedriving transistor DT. Further, the storage capacitor Cstg may beconnected between the first node N1 and the second node N2 of thedriving transistor DT, and may play the role of maintaining the datavoltage for one frame.

As described above, the sensing transistor SENT and the switchingtransistor SWT may be controlled by a single scan signal suppliedthrough the same gate line (common gate line). With regard to a singlescan structure based on 3T-1C, basically, the sensing transistor SENTmay be related to a “driving” so that the sensing transistor SENT mayapply a data voltage to the second node N2 of the driving transistor DT.Further, the switching transistor SWT may be related to a “sensing” inorder to compensate the difference of brightness between pixels as wellas the “driving.” Meanwhile, the pixel structure of the organic lightemitting display panel 140, according to an embodiment, may include a“signal line connection structure,” by which the pixel is connected withvarious signal lines, such as the data line DL, the gate line GL, thedriving voltage line DVL, the reference voltage line RVL, or the like,as well as the “basic pixel structure (single scan structure of 3T-1C),”as described in the FIG. 2 example.

In one example, the various signal lines may include the data line forsupplying the data voltage to each pixel, the gate line for supplyingthe scan signal, the reference voltage line (RVL) for supplying thereference voltage Vref to each pixel and the driving voltage line (DVL)for supplying the driving voltage EVDD. Meanwhile, the pixel structureof the organic light emitting display panel 140, according to anembodiment, is not limited to the above structures, and may beimplemented in various structures.

FIG. 4 illustrates a circuit diagram of a common part in various examplepixel structures of an organic light emitting display panel 140according to an embodiment.

The common part of the pixel structure is shown in FIGS. 2 and 3 and islabeled as “COMMON PART.” The configuration that is in common with thevarious pixel structures is illustrated in FIG. 4.

With reference to FIG. 4, the various pixel structures include thedriving transistor DT and the storage capacitor Cstg in common. Theupper plate or the lower plate of the storage capacitor Cstg may beconnected with the gate of the driving transistor DT, and the lowerplate or the upper plate of the storage capacitor Cstg may beelectrically connected with the source electrode or the drain electrodeof the driving transistor DT.

Until now, the examples of the pixel structures of the organic lightemitting display panel 140, to which embodiments are applied, have beendescribed. Hereinafter, the structure of the organic light emittingdisplay panel 140, according to embodiments, will be described infurther detail.

FIG. 5 is a partial plan view illustrating a pixel of an organic lightemitting display panel 140 according to an embodiment. FIG. 6illustrates a partial structure of the first plate 530 in the pixel ofthe organic light emitting display panel 140 of FIG. 5.

FIG. 5 shows the common part that is provided in various pixelstructures of the organic light emitting display panel 140. It should benoted that other elements may be designed in various structures.

With reference to the examples of FIGS. 5 and 6, the organic lightemitting display panel 140, according to an embodiment, may includepixels P that are defined by the respective intersections of a pluralityof data lines Dl to Dm and a plurality of gate lines Gl to Gn. Eachpixel P includes the transistor DT and the storage capacitor Cstg. Eachpixel P may further include a semiconductor layer 520, the first plate530 on the semiconductor layer 520 (which may be formed with a gateportion 530 a of the transistor DT and a capacitor-forming portion 530 bas the first electrode of the storage capacitor Cstg) and the secondplate 540 (which is the second electrode of the storage capacitor Cstgand does not overlap the semiconductor layer 520).

The gate portion 530 a of the first plate 530 may overlap thesemiconductor layer 520. The capacitor-forming portion 530 b of thefirst plate 530 may overlap the second plate 540. The gate portion 530 aand the capacitor-forming portion 530 b may form the storage capacitorCstg.

Meanwhile, the transistor DT may be the driving transistor DT fordriving the organic light emitting diode (OLED) in the pixel, butembodiments are not limited thereto. Although the structures of theillustrated embodiments show a top-gate type in which the gate portion530 a is positioned on the semiconductor layer 520, embodiments are notlimited thereto, and they may adopt a bottom-gate type.

The semiconductor layer 520 of the transistor DT may include an areathat is connected with the source electrode or the drain electrode 550and 550′ of the transistor DT and may include an active area or anactivation area. In addition, the semiconductor layer 520 may be formedfrom low temperature polysilicon. The semiconductor layer 520 of lowtemperature polysilicon has a low serial resistance in the active areaand gate insulator thereof can be formed to be thin. Therefore, in theorganic light emitting display panel 140 using the semiconductor layer520 of low temperature polysilicon, the driving circuit can be built inthe panel and the driving voltage may be relatively low to provide ahigh-resolution product.

Meanwhile, the gate portion 530 a of the first plate 530 may play therole of the gate electrode of the transistor DT. The gate portion 530 amay be formed to be integral with the capacitor-forming portion 530 band may overlap the semiconductor layer 520. That is, the first plate530 b may include the gate portion 530 a that overlaps the semiconductorlayer 520, and the capacitor-forming portion 530 b that overlaps thesecond plate 540. Further, the gate portion 530 a may be made, e.g., ofat least one of Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti,W, and Cu, or an alloy thereof, but embodiments are not limited thereto.

The first plate 530 and the second plate 540 thereon may form thestorage capacitor Cstg. For example, the first plate 530 may act as thefirst electrode of the storage capacitor Cstg, and the second plate 540may act as the second electrode of the storage capacitor Cstg. Thestorage capacitor Cstg may maintain the data voltage for one frame. Thesecond plate 540 may be made of at least one metal or an alloy.Meanwhile, although the structures of the semiconductor layer 520, thefirst plate 530, and the second plate 540 are illustrated in detail inFIG. 5 for the convenience of explanation, they may be variouslydesigned.

FIG. 7 is a partial sectional view of a pixel of an organic lightemitting display panel 140, along the lines A-A′ of FIG. 5, according toan embodiment.

With reference to the FIG. 7 example, the organic light emitting displaypanel 140, according to an embodiment, may include a plurality of pixelsP that may be defined by the respective intersections of a plurality ofdata lines and a plurality of gate lines. Each pixel P includes thetransistor DT and the storage capacitor Cstg of FIG. 5. Each pixel P mayfurther include a semiconductor layer 520, the first plate 530 on thesemiconductor layer 520 (which may be formed with a gate portion 530 aof the transistor DT and a capacitor-forming portion 530 b as the firstelectrode of the storage capacitor Cstg) and the second plate 540 on thefirst plate 530 (which may be the second electrode of the storagecapacitor Cstg and may not overlap the semiconductor layer 520).

In addition, the organic light emitting display panel 140 may furtherinclude the first insulator 522 formed between the semiconductor layer520 and the gate portion 530 a, the second insulator 532 formed betweenthe capacitor-forming portion 530 b and the second plate 540, and thethird insulator 542 formed on the second plate 540. Meanwhile, theorganic light emitting display panel 140 may further include the sourceelectrode or the drain electrode 550 of the transistor, which may beformed on the first plate 530 at the area opposite to the second plate540. Further, a flattening layer 560 may be formed to cover the thirdinsulator 542, the source electrode or the drain electrode 550.

As an example, the substrate 510 may be a plastic substrate, e.g.,polyethylene terephthalate (PET), polyethylennaphthalate (PEN), andpolyimide, or may be a glass substrate. A buffering layer (not shown)may be further provided on the first substrate 510 for preventingpenetration of impurities. For example, the buffering layer may beformed of a single layer or a multilayer of silicon nitrides or siliconoxides. In the case of the semiconductor layer 520 of low temperaturepolysilicon, the buffering layer may be made, e.g., of SiO₂ that has agood surface property. Meanwhile, the semiconductor layer 520 formed onthe substrate 510 may be made of low temperature polysilicon. It shouldbe appreciated that embodiments are not limited to these examplematerials.

At least one protrusion 500 may be formed on the surface of thesemiconductor layer 520. For example, the protrusions 500 may resultfrom the manufacturing process of low temperature polysilicon. As anexample, the low temperature polysilicon layer may be manufacturedthrough the process of depositing amorphous silicon on the substrate 510or the buffering layer by using plasma enhanced chemical vapordeposition (PECVD) and exposing the same to an excimer laser forre-crystallization. At this time, the protrusions 500 may stem from thegrains that are crystals of silicon, which may be captured on thesurface of the semiconductor layer, e.g., from the gain boundary of thegrains of the re-crystallized silicon. The protrusions 500 areillustrated for the convenience of explanation in FIG. 7, and the shape,the size or the number thereof may vary.

Meanwhile, the gate portion 530 a may be formed to correspond to theshape of the surface of the semiconductor layer 520. The gate portion530 a may be formed to conform to the shape of the protrusion 500 of thesemiconductor layer 520 by a deposition process. Also, the firstinsulator 522, the second insulator 532, and the third insulator 542 maybe made, e.g., of non-organic insulating materials, such as SiO_(x),SiN_(X), SiON, Al₂O₃, TiO₂, Ta₂O₅, HfO₂, ZrO₂, BST, and PZT, or organicinsulating materials including benzocyclobutene (BCB) and acryl-basedresin, or a combination thereof.

In addition to the above-described gate portion 530 a, the portions ofthe first insulator 522, the second insulator 532, and the thirdinsulator 542, which may overlap the semiconductor layer 520, may beformed to correspond to the shape of the surface of the semiconductorlayer 520. The first insulator 522, the second insulator 532, and thethird insulator 542 may be formed to be thin, e.g., by using chemicalvapor deposition (CVD) or physical vapor deposition (PVD), so thesurface shape of the lower layer may be reflected.

Meanwhile, the source electrode or the drain electrode 550 may be formedon the first plate 530 of the organic light emitting display panel 140at the area opposite to the second plate 540. That is, as shown in theexample of FIG. 7, the source electrode or the drain electrode may beformed at the area opposite to the area where the second plate 540 isformed, on the third insulator 542, with the semiconductor layer 520 atthe center. The source electrode or the drain electrode 550 may beformed to be a single layer or a multilayer made of one of, for example,Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, and Cu, or analloy thereof. For example, the source electrode or the drain electrodemay be made of metal having a high melting point, such as chromium (Cr)or tantalum (Ta), but it is not limited thereto.

The flattening layer 560 may be formed on the third insulator 542 andthe source electrode or the drain electrode 550, to flatten the pixel Pof the panel 140. Considering, for example, the mechanical strength, thepenetrating moisture proof, the easy formation of layers and theproductivity, the flattening layer 560 may be made of one of, e.g., aphoto acryl-based material, SiON, silicon nitrides (SiN_(x)), siliconoxides (SiO_(x)), and aluminum oxides (AlO_(x)), to be hydrophobic and ahydrogen-containing layer.

FIG. 8 is a partial sectional view of a pixel of an organic lightemitting display panel 140 according to an embodiment. FIG. 9 is apartial sectional view of a pixel of an organic light emitting displaypanel 140 according to an embodiment.

With reference to the examples of FIGS. 8 and 9, the organic lightemitting display panel 140, according to an embodiment, may include asemiconductor layer 520, a transistor DT including the first plate 530on the semiconductor layer 520, and the second plate 540 on the firstplate 530. The organic light emitting display panel 140 may furtherinclude the storage capacitor Cstg formed by the first plate 530 and thesecond plate 540, which overlap each other.

In one example, the transistor DT may be the driving transistor DT, butembodiments are not limited thereto. Further, the illustrated transistorDT may have a top-gate structure, but embodiments are not limitedthereto.

The semiconductor layer 520 of the transistor DT may include an areathat is connected with the source electrode or the drain electrode 550and 550′, and may include an active area or an activation area. Also,the semiconductor layer 520 may be made of low temperature polysilicon.

The second plate 540 of the organic light emitting display panel 140,according to an embodiment, overlaps the semiconductor layer 520 of thetransistor DT in part, and the first plate 530 and the second plate 540may entirely overlap each other. Accordingly, the capacitance of thestorage capacitor Cstg in the FIG. 8 example may become larger than inthe FIG. 5 example. Further, the area where the storage capacitor Cstgis formed except for the area where the transistor is formed may bereduced. As such, the non-aperture area may be reduced to enhance theaperture ratio.

FIGS. 10A and 10B illustrate partial sectional views of a structure ofthe second plate 540 in the pixel of the organic light emitting displaypanel 140 according to an embodiment.

With reference to the examples of FIGS. 10A and 10B, the organic lightemitting display panel 140, according to an embodiment, may include asemiconductor layer 520 formed on the substrate 510, a transistor DTincluding the first plate 530 on the semiconductor layer 520, and thesecond plate 540 on the first plate 530. In addition, the organic lightemitting display panel 140 may further include the first insulator 522formed between the semiconductor layer 520 and the gate portion 530 a,the second insulator 532 formed between the capacitor-forming portion530 b and the second plate 540, and the third insulator 542 formed onthe second plate 540. In one example, the transistor DT may be thedriving transistor or the low temperature polysilicon transistor (LTPSTFT).

FIG. 10A shows that the second plate 540 may not overlap thesemiconductor layer 520. FIG. 10B shows that the second plate 540 mayoverlap the semiconductor layer 520. The semiconductor layer 520 may bemade of low temperature polysilicon. In one example, a plurality ofprotrusions 500 may be formed, e.g., due to the grain boundary duringthe formation of the low temperature polysilicon, as set forth before.Accordingly, the thickness of the semiconductor layer 520 in the surfacedirection (longitudinal direction in the drawing) is not constant. Thatis, a curvature may be created on the surface of the semiconductor layer520, so the first plate 530, the first insulator 522, the secondinsulator 532, and the third insulator 542 may be formed to correspondto the surface shape of the semiconductor layer 520 at the portions thatoverlap the semiconductor layer 520.

In an example in which the second plate 540 overlaps the semiconductorlayer 520, the transistor DT may have degraded electrical properties.For example, the semiconductor layer 520 may be deteriorated so that amultitude of trapping sites, in which silicon atoms are disconnected,may be created in the silicon band gap, to degrade an electricalproperty thereof. As a result, this may bring about an increase inthreshold voltage and leakage current and a decrease in the field effectmobility. Further, the protrusions 500 may cause cracks in the firstplate 530, the insulators 522, 532, 542, and the second plate 540, anddegradation of the step coverage property. Consequently, when theorganic light emitting display panel 140 is turned on, the aboveproblems may result in the creation of a bunch of dark points to degradebrightness or a contrast ratio.

However, in an example in which the second plate 540 is formed to notoverlap the semiconductor layer 520, degradation of the electricproperty of the transistor due to the protrusions 500 may be prevented.Accordingly, the organic light emitting display panel 140 may beoperated at a low driving voltage with reduced leakage current tothereby prevent the creation of the dark points. Embodiments may preventdegradation of the electric property of the transistor to reduce thedriving voltage and leakage current and prevent the creation of theblack dots.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that embodiments of the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

What is claimed is:
 1. An organic light emitting display panel,comprising: a pixel defined by an intersection of one of a plurality ofdata lines and one of a plurality of gate lines, the pixel comprising: atransistor; a storage capacitor comprising: a first electrode; and asecond electrode; and a semiconductor layer; a first plate partiallyoverlapping the semiconductor layer in the pixel, the first platecomprising: a gate portion of the transistor; and a capacitor-formingportion comprising the first electrode of the storage capacitor; and asecond plate on the first plate in the pixel, the second platecomprising the second electrode of the storage capacitor, the secondplate not overlapping the semiconductor layer.
 2. The organic lightemitting display panel of claim 1, wherein: the gate portion of thefirst plate overlaps the semiconductor layer; and the capacitor-formingportion of the first plate overlaps the second plate to form the storagecapacitor.
 3. The organic light emitting display panel of claim 1,wherein the transistor comprises a driving transistor configured todrive an organic light emitting diode (OLED) in the pixel.
 4. Theorganic light emitting display panel of claim 1, wherein a sourceelectrode or a drain electrode of the transistor is formed on the firstplate at the area opposite to the second plate.
 5. The organic lightemitting display panel of claim 1, wherein the semiconductor layercomprises low temperature polysilicon.
 6. The organic light emittingdisplay panel of claim 1, wherein a surface of the semiconductor layercomprises at least one protrusion.
 7. The organic light emitting displaypanel of claim 6, wherein the at least one protrusion comprises grainscaptured on the surface of the semiconductor layer.
 8. The organic lightemitting display panel of claim 1, wherein the gate portion of the firstplate corresponds to the shape of the surface of the semiconductorlayer.
 9. The organic light emitting display panel of claim 1, furthercomprising: a first insulator between the semiconductor layer and thegate portion; a second insulator between the capacitor-forming portionand the second plate; and a third insulator on the second plate.
 10. Theorganic light emitting display panel of claim 9, wherein portions of thefirst insulator, the second insulator, and the third insulator, whichoverlap the semiconductor layer, correspond to the shape of the surfaceof the semiconductor layer.
 11. A method of manufacturing an organiclight emitting display panel, the method comprising: providing a pixeldefined by an intersection of one of a plurality of data lines and oneof a plurality of gate lines, the providing the pixel comprising:providing a transistor; providing a storage capacitor comprising: afirst electrode; and a second electrode; and providing a semiconductorlayer; providing a first plate partially overlapping the semiconductorlayer in the pixel, the providing a first plate comprising: providing agate portion of the transistor; and providing a capacitor-formingportion comprising the first electrode of the storage capacitor; andproviding a second plate on the first plate in the pixel, the secondplate comprising the second electrode of the storage capacitor, thesecond plate not overlapping the semiconductor layer.
 12. The method ofclaim 11, wherein: the gate portion of the first plate overlaps thesemiconductor layer; and the capacitor-forming portion of the firstplate overlaps the second plate to form the storage capacitor.
 13. Themethod of claim 11, wherein the transistor comprises a drivingtransistor for driving an organic light emitting diode (OLED) in thepixel.
 14. The method of claim 11, wherein a source electrode or a drainelectrode of the transistor is provided on the first plate at the areaopposite to the second plate.
 15. The method of claim 11, wherein thesemiconductor layer comprises low temperature polysilicon.
 16. Themethod of claim 11, wherein at least one protrusion is provided on thesurface of the semiconductor layer.
 17. The method of claim 16, whereinthe at least one protrusion is formed by grains captured on the surfaceof the semiconductor layer.
 18. The method of claim 11, wherein the gateportion of the first plate is provided to correspond to the shape of thesurface of the semiconductor layer.
 19. The method of claim 11, furthercomprising: providing a first insulator between the semiconductor layerand the gate portion; providing a second insulator between thecapacitor-forming portion and the second plate; and providing a thirdinsulator on the second plate.
 20. The method of claim 19, whereinportions of the first insulator, the second insulator, and the thirdinsulator, which overlap the semiconductor layer, are provided tocorrespond to the shape of the surface of the semiconductor layer.